Transmissions generally include a number of gear elements and torque establishing devices such as clutches and brakes. The clutches and brakes are selectively engageable to activate certain gear elements. Gear elements are activated to establish a desired speed or gear ratio between a transmission input shaft and a transmission output shaft.
The transmission input shaft may be connected to an engine through a fluid coupling such as a torque converter. The transmission output shaft is connected to vehicle wheels. Shifting from one gear ratio to another may be performed in response to changes in throttle position and vehicle speed. Alternatively, a driver may specifically command a shift between gear ratios.
A shift from one gear element to another may be an upshift (i.e., a shift to a higher gear) or a downshift (i.e., a shift to a lower gear). The shift may be further defined as a power-on shift (i.e., a shift that occurs when an accelerator pedal is depressed) or a power-off shift (i.e., a shift that occurs when an accelerator pedal is released).
Some shift operations may use positive torque management to complete the shift operation. Positive torque management is defined as the transmission sending a torque increase request to the engine, and the engine honors the request and increases torque production, in order to complete a shift operation.